1. Field of the Invention
This invention relates to differential amplifier compensation. Particularly, it relates to increasing the common mode rejection ratio of differential amplifiers. More particularly, it relates to the compensation of differential amplifiers to correct for offset voltages due to unbalance in amplifier component parameters.
2. Description of the Related Art
In the prior art, input offset voltages of differential amplifiers used as signal level detectors are reduced by increasing the size of input devices which in effect reduces their bandwidth because of the parasitic capacitance of the larger devices.
Another prior art approach to reducing offset voltages is to adjust the common mode voltage of the differential amplifier. This reduces the sensitivity for the amplifiers' use as signal level detectors and complicates the amplifier design by having to implement additional circuitry for common mode compensation.
A further prior art approach is to compensate the offset voltage by the addition of an offset voltage at the single-ended input of the differential amplifier. While compensating for the offset voltage, however, the common mode voltage of the differential amplifier will vary. This reduces the sensitivity for the differential amplifiers' use as signal level detectors and complicates the amplifier design by the necessity to implement provisions of additional circuitry for common mode signal regulation.